In the prior art, the handle and the head of a hand tool are arranged at the same plane and the handle is non-rotatable with respect to the head so that the orientation of the head with respect to the handle is unadjustable. However if the work environment is not so suitable for locating the hand tool, the hand tool cannot be operated conveniently.
Therefore, in one improvement, the head is folded with respect to the handle with a predetermined angle. However the bending angle between the handle and the head is fixed, Thus it is only suitable for some specific work environments.
Thus there are other hand tools being developed for overcoming the defect in the prior art designs, however all these hand tools can only make the head pivotally rotates with respect to the handle in one orientation, but it cannot rotate along a different orientation. Thereby the head is fixedly installed to the handle. It is un-replaceable. Thus if the driven object (for example a screw) is not suitable for the hand tool, another kind of hand tool must be prepared. Thus the use of the prior art is limited.